What Is The Package?
The package is a Java namespace or part of Java libraries. The Java API is grouped into libraries of related classes and interfaces; these libraries are known as packages.
What Is Native Code?
The native code is a code that after you compile it, the compiled code runs on a specific hardware platform.
Is Java Code Slower Than Native Code?
Not really. As a platform-independent environment, the Java platform can be a bit slower than native code. However, smart compilers, well-tuned interpreters, and just-in-time bytecode compilers can bring performance close to that of native code without threatening portability.
What Is The Serialization?
The serialization is a kind of mechanism that makes a class or a bean persistence by having its properties or fields and state information saved and restored to and from storage.
How To Make A Class Or A Bean Serializable?
By implementing either the java.io.Serializable interface or the java.io.Externalizable interface. As long as one class in a class's inheritance hierarchy implements Serializable or Externalizable, that class is serializable.
How Many Methods Are There In The Serializable Interface?
There is no method in the Serializable interface. The Serializable interface acts as a marker, telling the object serialization tools that your class is serializable.
How Many Methods Are There In The Externalizable Interface?
There are two methods in the Externalizable interface. You have to implement these two methods in order to make your class externalizable. These two methods are
readExternal() and
writeExternal().
Which Containers Use A Border Layout As Their Default Layout?
The Window, Frame and Dialog classes use a border layout as their default layout.
What Is Synchronization And Why Is It Important?
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often causes dirty data and leads to significant errors.
What Are Three Ways In Which A Thread Can Enter The Waiting State?
A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.
What Is The Preferred Size Of A Component?
The preferred size of a component is the minimum component size that will allow the component to display normally.
Can Java Object Be Locked Down For Exclusive Use By A Given Thread?
Yes. You can lock an object by putting it in a "synchronized" block. The locked object is inaccessible to any thread other than the one that explicitly claimed it.
Can Each Java Object Keep Track Of All The Threads That Want To Exclusively Access It?
Yes.
What Is The Purpose Of The Wait(), Notify() And Notifyall() Methods?
The wait(), notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.
What Are The High-level Thread States?
The high-level thread states are ready, running, waiting and dead.
What Is The Collections Api?
The Collections API is a set of classes and interfaces that support operations on collections of objects.
What Is The List Interface?
The List interface provides support for ordered collections of objects.
How Many Bits Are Used To Represent Unicode, Ascii, Utf-16 And Utf-8 Characters?
Unicode requires 16 bits.
ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits.
UTF-8 represents characters using 8, 16, and 18 bit patterns.
UTF-16 uses 16-bit and larger bit patterns.
What Is The Properties Class?
The properties class is a subclass of Hashtable that can be read from or written to a stream. It also provides the capability to specify a set of default values to be used.
What Is The Purpose Of The Runtime Class?
The purpose of the Runtime class is to provide access to the Java runtime system.
What Is The Purpose Of The Finally Clause Of A Try-catch-finally Statement?
The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.
What Is The Locale Class?
The Locale class is used to tailor program output to the conventions of a particular geographic, political or cultural region.
What Is A Protected Method?
A protected method is a method that can be accessed by any method in its package and inherited by any subclass of its class.
What Is A Static Method?
A static method is a method that belongs to the class rather than any object of the class and doesn't apply to an object or even require that any objects of the class have been instantiated.
What Is The Difference Between A Window And A Frame?
A frame is a resizable, movable window with title bar and close button. Usually it contains Panels. Its derived from a window and has a borderlayout by default.
A window is a Container and has BorderLayout by default. A window must have a parent Frame mentioned in the constructor.
What Are Peerless Components?
The peerless components are called light weight components.
What Is The Difference Between The Reader/writer Class Hierarchy And The Inputstream/outputstream Class Hierarchy?
The Reader/Writer class hierarchy is character-oriented and the InputStream/OutputStream class hierarchy is byte-oriented.
What Is The Difference Between Throw And Throws Keywords?
The throw keyword denotes a statement that causes an exception to be initiated. It takes the Exception object to be thrown as argument. The exception will be caught by an immediately encompassing try-catch construction or propagated further up the calling hierarchy. The throws keyword is a modifier of a method that designates that exceptions may come out of the method, either by virtue of the method throwing the exception itself or because it fails to catch such exceptions that a method it calls may throw.
Name Primitive Java Types?
The primitive Java types are byte, char, short, int, long, float, double and boolean.
How Can A Gui Component Handle Its Own Events?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
What Advantage Do Java's Layout Managers Provide Over Traditional Windowing Systems?
Java uses layout managers to layout components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accommodate platform-specific differences among windowing systems.
What Are The Problems Faced By Java Programmers Who Don't Use Layout Managers?
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.
What Is The Difference Between Static And Non-static Variables?
A static variable is associated with the class as a whole, rather than with specific instances of a class. Non-static variables take on unique values with each object instance.
What Is The Difference Between The Paint() And Repaint() Methods?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
What Is A Container In A Gui?
A Container contains and arranges other components (including other containers) through the use of layout managers, which use specific layout policies to determine where components should go as a function of the size of the container.
Is Iterator A Class Or Interface? What Is Its Use?
Iterator is an interface which is used to step through the elements of a Collection.
How You Can Force The Garbage Collection?
Garbage collection is an automatic process and can't be forced.
Describe The Principles Of Oops?
There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.
Explain The Encapsulation Principle?
Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by the other code defined outside the wrapper.
Explain The Inheritance Principle?
Inheritance is the process by which one object acquires the properties of another object.
How To Define An Abstract Class?
A class containing abstract method is called Abstract class. An Abstract class can't be instantiated.
Example of Abstract class: abstract
class testAbstractClass {
protected String myString;
public String getMyString() { return myString;
}
public abstract string anyAbstractFunction{);
}
How To Define An Interface?
In Java, Interface defines the methods but does not implement them. Interface can include constants. A class that implements the interfaces is bound to implement all the methods defined in Interface.
Example of Interface
public interface samplelnterface {
public void functionOne();
public long CONSTANTJDNE = 1000;
}
Explain The Polymorphism Principle?
The meaning of Polymorphism is something like one name, many forms. Polymorphism enables one entity to be used as a general category for different types of actions. The specific action is determined by the exact nature of the situation. The concept of polymorphism can be explained as "one interface, multiple methods".
Explain The Different Forms Of Polymorphism?
From a practical programming viewpoint, polymorphism exists in three distinct forms in Java
Method overloading
Method overriding through inheritance
Method overriding through the Java interface.
The package is a Java namespace or part of Java libraries. The Java API is grouped into libraries of related classes and interfaces; these libraries are known as packages.
What Is Native Code?
The native code is a code that after you compile it, the compiled code runs on a specific hardware platform.
Is Java Code Slower Than Native Code?
Not really. As a platform-independent environment, the Java platform can be a bit slower than native code. However, smart compilers, well-tuned interpreters, and just-in-time bytecode compilers can bring performance close to that of native code without threatening portability.
What Is The Serialization?
The serialization is a kind of mechanism that makes a class or a bean persistence by having its properties or fields and state information saved and restored to and from storage.
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| Adobe Systems Most Frequently Asked Latest Core Java Interview Questions Answers |
How To Make A Class Or A Bean Serializable?
By implementing either the java.io.Serializable interface or the java.io.Externalizable interface. As long as one class in a class's inheritance hierarchy implements Serializable or Externalizable, that class is serializable.
How Many Methods Are There In The Serializable Interface?
There is no method in the Serializable interface. The Serializable interface acts as a marker, telling the object serialization tools that your class is serializable.
How Many Methods Are There In The Externalizable Interface?
There are two methods in the Externalizable interface. You have to implement these two methods in order to make your class externalizable. These two methods are
readExternal() and
writeExternal().
Which Containers Use A Border Layout As Their Default Layout?
The Window, Frame and Dialog classes use a border layout as their default layout.
What Is Synchronization And Why Is It Important?
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often causes dirty data and leads to significant errors.
What Are Three Ways In Which A Thread Can Enter The Waiting State?
A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.
What Is The Preferred Size Of A Component?
The preferred size of a component is the minimum component size that will allow the component to display normally.
Can Java Object Be Locked Down For Exclusive Use By A Given Thread?
Yes. You can lock an object by putting it in a "synchronized" block. The locked object is inaccessible to any thread other than the one that explicitly claimed it.
Can Each Java Object Keep Track Of All The Threads That Want To Exclusively Access It?
Yes.
What Is The Purpose Of The Wait(), Notify() And Notifyall() Methods?
The wait(), notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.
What Are The High-level Thread States?
The high-level thread states are ready, running, waiting and dead.
What Is The Collections Api?
The Collections API is a set of classes and interfaces that support operations on collections of objects.
What Is The List Interface?
The List interface provides support for ordered collections of objects.
How Many Bits Are Used To Represent Unicode, Ascii, Utf-16 And Utf-8 Characters?
Unicode requires 16 bits.
ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits.
UTF-8 represents characters using 8, 16, and 18 bit patterns.
UTF-16 uses 16-bit and larger bit patterns.
What Is The Properties Class?
The properties class is a subclass of Hashtable that can be read from or written to a stream. It also provides the capability to specify a set of default values to be used.
What Is The Purpose Of The Runtime Class?
The purpose of the Runtime class is to provide access to the Java runtime system.
What Is The Purpose Of The Finally Clause Of A Try-catch-finally Statement?
The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.
What Is The Locale Class?
The Locale class is used to tailor program output to the conventions of a particular geographic, political or cultural region.
What Is A Protected Method?
A protected method is a method that can be accessed by any method in its package and inherited by any subclass of its class.
What Is A Static Method?
A static method is a method that belongs to the class rather than any object of the class and doesn't apply to an object or even require that any objects of the class have been instantiated.
What Is The Difference Between A Window And A Frame?
A frame is a resizable, movable window with title bar and close button. Usually it contains Panels. Its derived from a window and has a borderlayout by default.
A window is a Container and has BorderLayout by default. A window must have a parent Frame mentioned in the constructor.
What Are Peerless Components?
The peerless components are called light weight components.
What Is The Difference Between The Reader/writer Class Hierarchy And The Inputstream/outputstream Class Hierarchy?
The Reader/Writer class hierarchy is character-oriented and the InputStream/OutputStream class hierarchy is byte-oriented.
What Is The Difference Between Throw And Throws Keywords?
The throw keyword denotes a statement that causes an exception to be initiated. It takes the Exception object to be thrown as argument. The exception will be caught by an immediately encompassing try-catch construction or propagated further up the calling hierarchy. The throws keyword is a modifier of a method that designates that exceptions may come out of the method, either by virtue of the method throwing the exception itself or because it fails to catch such exceptions that a method it calls may throw.
Name Primitive Java Types?
The primitive Java types are byte, char, short, int, long, float, double and boolean.
How Can A Gui Component Handle Its Own Events?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
What Advantage Do Java's Layout Managers Provide Over Traditional Windowing Systems?
Java uses layout managers to layout components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accommodate platform-specific differences among windowing systems.
What Are The Problems Faced By Java Programmers Who Don't Use Layout Managers?
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.
What Is The Difference Between Static And Non-static Variables?
A static variable is associated with the class as a whole, rather than with specific instances of a class. Non-static variables take on unique values with each object instance.
What Is The Difference Between The Paint() And Repaint() Methods?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
What Is A Container In A Gui?
A Container contains and arranges other components (including other containers) through the use of layout managers, which use specific layout policies to determine where components should go as a function of the size of the container.
Is Iterator A Class Or Interface? What Is Its Use?
Iterator is an interface which is used to step through the elements of a Collection.
How You Can Force The Garbage Collection?
Garbage collection is an automatic process and can't be forced.
Describe The Principles Of Oops?
There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.
Explain The Encapsulation Principle?
Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by the other code defined outside the wrapper.
Explain The Inheritance Principle?
Inheritance is the process by which one object acquires the properties of another object.
How To Define An Abstract Class?
A class containing abstract method is called Abstract class. An Abstract class can't be instantiated.
Example of Abstract class: abstract
class testAbstractClass {
protected String myString;
public String getMyString() { return myString;
}
public abstract string anyAbstractFunction{);
}
How To Define An Interface?
In Java, Interface defines the methods but does not implement them. Interface can include constants. A class that implements the interfaces is bound to implement all the methods defined in Interface.
Example of Interface
public interface samplelnterface {
public void functionOne();
public long CONSTANTJDNE = 1000;
}
Explain The Polymorphism Principle?
The meaning of Polymorphism is something like one name, many forms. Polymorphism enables one entity to be used as a general category for different types of actions. The specific action is determined by the exact nature of the situation. The concept of polymorphism can be explained as "one interface, multiple methods".
Explain The Different Forms Of Polymorphism?
From a practical programming viewpoint, polymorphism exists in three distinct forms in Java
Method overloading
Method overriding through inheritance
Method overriding through the Java interface.
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